Polyisocyanate composition and coating with improved chemical resistance

Abstract

The invention relates to the field of polyisocyanate compositions, and provides a polyisocyanate composition and a coating with improved chemical resistance, the coating formed by a polyurethane coating composition based on the polyisocyanate composition provided by the invention has significantly improved chemical resistance, and the coating has excellent corrosion resistance and corrosion resistance. And comprehensive properties such as good hardness and bending strength can be considered. The polyisocyanate composition is derived from at least one diisocyanate selected from aliphatic diisocyanate and alicyclic diisocyanate, and in compounds contained in the polyisocyanate composition, at least part of the compounds have isocyanurate groups, and at least part of the compounds have isocyanate groups. And at least part of the compound has at least one thioallophanate group; in the polyisocyanate composition, the equivalence ratio of the thioallophanate group to the isocyanurate group is greater than 0 and less than or equal to 0.3.

Description

Technical Field

[0001] The present invention relates to a polyisocyanate composition, and more particularly to a polyisocyanate composition and a coating with improved chemical resistance. Background Art

[0002] Aliphatic / alicyclic polyisocyanates have excellent properties such as weather resistance, wear resistance, and corrosion resistance, and are widely used in the coatings, adhesives, and elastomer industries, especially in the paint industry, including the most widely used polyisocyanate curing agents containing isocyanate groups.

[0003] Aliphatic polyisocyanate compositions containing isocyanurate groups have excellent yellowing resistance, and in addition, have the advantages of low free monomer content, saturated vapor concentration far below the occupational safety limit, high functionality, and large downstream crosslinking density. At present, a large number of documents and patents have reported methods for preparing polyisocyanate compositions containing isocyanurate from aliphatic and alicyclic diisocyanates under the action of catalysts (e.g., J. Prakt. Chem. 336 (1994) 185-200, US Pat. No. 4,040,992, US Pat. No. 4,288,586, US Pat. No. 4,419,513, US Pat. No. 6,730,62, US Pat. No. 6,800,714, US Pat. No. 7,001,973, etc.).

[0004] In view of the diversity of downstream application formulation systems, curing agents often need to be used in combination with high-hydroxyl resins to improve the crosslinking density, mechanical properties and chemical resistance of the paint film. However, due to the rigid structure of the isocyanurate ring itself, it has poor compatibility in the high-hydroxyl resin formulation system, resulting in the composition being thin and turbid, with a blue glow, etc., which affects the glossiness of the formed paint film. Currently, the main way to improve the compatibility of polyisocyanate compositions is alcohol modification, that is, introducing alcohol into the system.

[0005] US460441 reports a polyisocyanate composition containing isocyanurate modified by the polymerization of polyisocyanate with diol or polyol to form urea ester.

[0006] US6420508 discloses a two-step method of synthesizing a polyisocyanate composition with good compatibility by first self-polymerizing the polyisocyanate and then performing alcohol modification.

[0007] CN1074065 prepares a polyisocyanate composition, controls the isocyanurate trimer content to be ≤59% and the equivalent ratio of allophanate group to isocyanurate group to be >0 and ≤0.19, and has good compatibility.

[0008] Although the problem of compatibility can be partially solved by alcohol modification, the composition obtained by this route often has disadvantages such as low isocyanate group concentration resulting in high amount of curing agent, and poor chemical resistance after film formation of the composition. Summary of the invention

[0009] The present invention provides a polyisocyanate composition and a coating with improved chemical resistance. The coating formed by the polyurethane coating composition based on the polyisocyanate composition provided by the present invention has significantly improved chemical resistance and can take into account good hardness and bending strength.

[0010] To achieve the purpose, the present invention provides the following technical solutions:

[0011] On one hand, the present invention provides a polyisocyanate composition, which is derived from at least one diisocyanate selected from aliphatic diisocyanates and alicyclic diisocyanates, wherein at least some of the compounds contained in the polyisocyanate composition have isocyanurate groups, and at least some of the compounds have at least one thioalloyphanate group; in the polyisocyanate composition, the equivalent ratio of the thioalloyphanate group to the isocyanurate group is greater than 0 and less than or equal to 0.3, for example, 0.001, 0.003, 0.005, 0.007, 0.010, 0.015, 0.020, 0.025, 0.030, 0.050, 0.070, 0.100, 0.150, 0.200, 0.250, 0.270, 0.300, etc.

[0012] The present inventors unexpectedly found that by controlling the equivalent ratio of the thioalloycarboxate group to the isocyanurate group in the polyisocyanate composition to be greater than 0 and less than or equal to 0.3, the chemical resistance of the polyurethane coating based on the polyisocyanate composition can be improved while achieving good hardness and flexural strength.

[0013] Preferably, in the polyisocyanate composition, the equivalent ratio of the thioalleophanate group to the isocyanurate group is 0.005-0.250. More preferably, the equivalent ratio of the thioalleophanate group to the isocyanurate group is 0.005-0.100. Controlling the equivalent ratio of the polyisocyanate composition within a preferred range is beneficial to further improve the coating properties of the obtained polyurethane coating, while taking into account more excellent chemical resistance, hardness and bending strength.

[0014] In the present invention, the isocyanurate group refers to a group having the following structural units:

[0015]

[0016] In the present invention, the thioallophonate group refers to a group having the following structural units:

[0017]

[0018] The thiourea carboxylate groups are distributed in polymers such as trimers, pentamers, heptamers and / or nonamers during the trimerization process.

[0019] In the present invention, the polyisocyanate composition, in addition to isocyanurate groups and thioalloylate groups, optionally contains (i.e., contains or does not contain) one or more of iminooxadiazinedione groups, biuret groups, uretdione groups, thiocarbamate groups, and uretonimine groups.

[0020] Wherein, the iminooxadiazinedione group refers to a group having the following structural units:

[0021]

[0022] A biuret group is a group having the following structural units:

[0023]

[0024] A uretdione group is a group having the following structural units:

[0025]

[0026] Thiocarbamate groups are groups having the following structural units:

[0027]

[0028] Uretonimine group refers to a group having the following structural units:

[0029]

[0030] The above structural units can all be detected by nuclear magnetic resonance carbon spectroscopy.

[0031] In the polyisocyanate composition, the content of the isocyanurate group is ≥90 mol% and <100 mol%, based on the total amount of the isocyanurate group and the thioalloyphanate group in the composition and the optionally present (i.e., present or absent) iminooxadiazinedione group, biuret group, uretdione group, thiocarbamate group and uretonimine group. When the iminooxadiazinedione group, biuret group, uretdione group, thiocarbamate group and / or uretonimine group are present, they are included in the total amount; when they are not present, their amount is 0. The content of the isocyanurate group is, for example, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 99.5%, etc.

[0032] Further, the polyisocyanate composition can be obtained by reacting a reaction mass comprising a diisocyanate and a thiol compound, wherein the thiol compound is selected from at least one linear or branched and optionally substituted thiol compound. Preferably, the group reactive to the isocyanate group in the thiol compound is a thiol group, and specifically, the thiol compound contains no other groups reactive to the isocyanate group except the thiol group. In some embodiments, for example, the thiol compound is inert to the isocyanate group in the side chain.

[0033] Preferably, the thiol compound has 1-20 carbon atoms, preferably 6-12 carbon atoms; the thiol compound may be one or more of monothiol and polythiol. More preferably, the thiol compound is a monothiol, for example, a monothiol with 6-12 carbon atoms; the inventors have found that the use of a monothiol can better improve the performance of the coating in the subsequent polyurethane coating compared to the polyisocyanate composition obtained by using a polythiol, and can not only take into account excellent chemical resistance, hardness and bending strength, but also excellent adhesion. Among them, the monohydric mercaptan is preferably selected from one or more of 1-hexyl mercaptan, 2-hexyl mercaptan, 3-hexyl mercaptan, 1-methylpentane-2-mercaptan, 3,3-dimethylbutane-1-mercaptan, 2-ethyl-butane-1-mercaptan, 1-methyl-1-pentane mercaptan, 3-methylpentane-2-mercaptan, 1-heptyl mercaptan, 2-heptyl mercaptan, 1-octan mercaptan, 2-octan mercaptan, 2-ethyl-1-hexyl mercaptan, 1-nonyl mercaptan, 2-nonyl mercaptan, 1-decyl mercaptan, 3-decyl mercaptan, 1-undecanethiol, undec-10-ene-1-mercaptan, 1-dodecyl mercaptan, 2-dodecyl mercaptan, and tert-dodecyl mercaptan.

[0034] The polythiol may be ethylene glycol bis(3-mercaptopropionate), butanedithiol, propanedithiol, 1,5-pentanedithiol, propane-1,2,3-trithiol, trimethylolpropane tris(3-mercaptopropionate), pentaerythritol tetrakis(3-mercaptopropionate), or the like.

[0035] The polyisocyanate composition of the present invention is derived from aliphatic diisocyanate and / or alicyclic diisocyanate. Wherein, "derived from aliphatic diisocyanate and / or alicyclic diisocyanate" means that the main raw materials used to prepare the polyisocyanate composition at least include aliphatic diisocyanate and / or alicyclic diisocyanate. The aliphatic diisocyanate and / or alicyclic diisocyanate used in the preparation process is selected from one or more of hexamethylene diisocyanate (HDI), pentamethylene diisocyanate (PDI), 2-methylpentane-1,5-diisocyanate, 2,4,4-trimethyl-1,6-hexane diisocyanate, 2,2,4-trimethyl-1,6-hexane diisocyanate, 4-isocyanatomethyl-1,8-octane diisocyanate, 3-isocyanatomethyl-1-methylcyclohexyl isocyanate (IMCI), 4-isocyanatomethyl-1-methylcyclohexyl isocyanate (IMCI), isophorone diisocyanate (IPDI), 1,3-bis(isocyanatomethyl)cyclohexane and 1,4-bis(isocyanatomethyl)cyclohexane (H6XDI), preferably one or two of hexamethylene diisocyanate (HDI) and pentamethylene diisocyanate (PDI).

[0036] The reaction is carried out in the presence of a catalyst.

[0037] The catalyst is preferably selected from one or more of quaternary ammonium hydroxides, quaternary ammonium carboxylates, compounds containing aminosilyl groups, tertiary amine compounds, and Mannich base compounds. The quaternary ammonium hydroxide is, for example, selected from one or more of tetramethylammonium hydroxide, trimethylbenzylammonium hydroxide, tetraethylammonium hydroxide, dimethylethylcyclohexylammonium hydroxide, and hydrates thereof, preferably one or more of tetramethylammonium hydroxide and trimethylbenzylammonium hydroxide, and hydrates thereof. The quaternary ammonium carboxylate is selected from, for example, tetramethylammonium hydroxide-2-ethylhexanoate, tetramethylammonium hydroxide-octanoate, trimethylbenzylammonium hydroxide-2-ethylhexanoate, trimethylbenzylammonium hydroxide-octanoate, tetramethylammonium hydroxide-formate, tetramethylammonium hydroxide-acetate, tetramethylammonium hydroxide-pivalate, trimethylbenzylammonium hydroxide-pivalate, tetramethylammonium hydroxide-decanoate, trimethylbenzylammonium hydroxide-decanoate, tetramethylammonium hydroxide-tetradecanoate, tetramethylammonium hydroxide-2-ethylhexanoate, tetramethylammonium hydroxide-octanoate, trimethylbenzylammonium hydroxide-2-ethylhexanoate, and one or more of trimethylbenzylammonium hydroxide-octanoate. The aminosilyl-containing compound is selected from, for example, one or more of hexamethyldisilazane, silylamine, and heptamethyldisilazane, preferably hexamethyldisilazane. Further, the tertiary amine compound is, for example, one or two of triethylamine and tripropylamine, preferably triethylamine; Mannich base compounds are, for example, tris(N,N-dimethylaminomethyl)phenol, etc. The inventors have found that the use of the above-mentioned preferred catalyst without metal elements is conducive to obtaining a polyisocyanate composition that meets the equivalent ratio of thiourea carboxylate groups to isocyanurate groups required in the present invention, and in particular, the target product can be obtained at a relatively low reaction temperature, for example, the target product of the present invention can be obtained at a reaction temperature not exceeding 80°C (e.g., 30-79°C, e.g., 45-75°C). In the present invention, the catalyst can be used as a pure substance or optionally dissolved in a solvent at any concentration. The amount of the catalyst added is preferably 0.001-0.1wt% of the amount of the starting diisocyanate used to prepare the polyisocyanate composition, such as 0.001wt%, 0.005wt%, 0.01wt%, 0.05wt%, 0.1wt%, etc., preferably 0.005-0.05wt%; the preferred catalyst amount is used to obtain a polyisocyanate composition that meets the equivalent ratio of thiourea carboxylate groups to isocyanurate groups required in the present invention.

[0038] In some preferred embodiments, when a polyisocyanate composition is prepared by reacting a starting diisocyanate and a thiol compound in the presence of a catalyst, the reaction temperature can be 10-150°C, for example, 10°C, 30°C, 50°C, 100°C, 120°C, 150°C, etc., preferably 30-79°C, more preferably 45-75°C. Reacting at a preferred temperature is conducive to obtaining a polyisocyanate composition that meets the equivalent ratio of thioalloycarboxylate groups to isocyanurate groups required by the present invention, and can also take into account good operational safety.

[0039] The polyisocyanate composition satisfying the required equivalent ratio of thioalloylate groups to isocyanurate groups in the present invention can be obtained by adjusting the amounts of diisocyanate and mercapto compound, the NCO% value of the reaction system at the reaction end point, the type and amount of catalyst, and / or the reaction temperature.

[0040] In some embodiments, in the reaction system for preparing the polyisocyanate composition, the amount of diisocyanate and the thiol compound is such that the equivalent ratio of the thiol provided by the thiol compound to the isocyanate provided by the diisocyanate is greater than 0 and ≤ 0.06, such as 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, etc. The specific amount of diisocyanate and the thiol compound is based on the equivalent ratio of the thioalloylate group to the isocyanurate group in the prepared polyisocyanate composition meeting the requirements of the present invention.

[0041] During the reaction process of preparing the polyisocyanate composition, the NCO% value of the reaction system is monitored. Preferably, the reaction endpoint of the reaction is that the NCO% value of the reaction system is in the range of 30-50%, such as 30%, 35%, 37%, 40%, 45%, 47%, 50%, etc. When the reaction system reaches the target NCO%, the polymerization reaction is terminated. The inventors have found that when the NCO% value is greater than 50%, it often leads to problems such as low conversion rate, large monomer consumption and increased energy consumption required for subsequent monomer removal, and low functionality of the composition; when the NCO% value is less than 30%, the viscosity of the polyisocyanate composition is too large, which has an adverse effect on the convenience of downstream construction and the leveling of the paint film. Specifically, the polymerization reaction can be terminated by adding a catalyst poison to the reaction system. As a catalyst poison, an acidic reactive substance such as a protonic acid (for example, dibutyl phosphate), or an acylating agent (for example, isophthalic acid dichloride) and the like can be considered. In some examples, the catalyst poison is selected from one or more of protonic acid and acylating agent, preferably one or more of phosphoric acid, benzoic acid, diisooctyl phosphate and dibutyl phosphate. It will be appreciated by those skilled in the art that different types of polymerization catalysts used in the reaction system will result in different amounts of catalyst poisons. In the reaction system of the present invention, the amount of catalyst poison added is based on the inactivation of the polymerization catalyst in the system.

[0042] In the present invention, the unreacted monomers (diisocyanates) can be removed by treating the reaction solution obtained by preparing the polyisocyanate composition with a single-stage or multi-stage thin film evaporator. Specifically, for example, after the treatment, the residual monomer content in the polyisocyanate composition is less than 0.5 wt % based on the mass of the composition.

[0043] In some embodiments, the viscosity of the polyisocyanate composition provided by the present invention is 2000-20000cp / 25°C, for example, 2000, 2500, 3000, 5000, 7000, 9000, 10000, 15000, 20000cp / 25°C, etc., for example, 2000-15000cp / 25°C, and the isocyanate group content is 20-25%.

[0044] The inventors have found that, in a polyisocyanate composition obtained by reacting an aliphatic diisocyanate and / or an alicyclic diisocyanate with a monohydric thiol, under substantially the same other conditions, a polyisocyanate composition satisfying an equivalent ratio of thiourea carboxylate group to isocyanurate group of >0 and ≤0.3 can obtain a coating having better pendulum hardness, chemical resistance, bending strength and other comprehensive properties than a polyisocyanate composition not satisfying the equivalent ratio, especially a two-component polyurethane coating system formed by an adhesive reactive with isocyanate groups. Among them, the adhesive reactive with isocyanate groups can be a type commonly used in the field of polyurethane coatings, for example, it can be one or more of polyether polyols, polyester polyols, polyurethane polyols, polysiloxane polyols, polycarbonate polyols, polyether polyamines, polyaspartic acid, polybutadiene polyols, polyacrylate polyols, polyacrylic acid polyols, etc.

[0045] In the present invention, the NCO content (NCO%) is determined according to the method of GB / T 12009.4-2016, wherein NCO% refers to the mass percentage of isocyanate. The viscosity is measured using a BrookField DVI Prime viscometer with an S21 rotor at 25°C.

[0046] The present invention also provides use of the polyisocyanate composition described above as a crosslinking agent in a coating composition.

[0047] The present invention also provides a two-component polyurethane coating composition, comprising component A and component B, wherein component A comprises at least one polyisocyanate composition described above, and component B comprises at least one adhesive reactive to isocyanate groups. Regarding the two-component polyurethane coating composition, in addition to the polyisocyanate composition provided in the present invention, the remaining components and / or the amount of each component can be selected conventionally in the two-component polyurethane coating composition, and there is no particular restriction on this. Specifically, the above-mentioned adhesive reactive to isocyanate groups is a hydroxyl resin. In some embodiments, the adhesive reactive to isocyanate groups is one or more of polyether polyols, polyester polyols, polyurethane polyols, polysiloxane polyols, polycarbonate polyols, polyether polyamines, polyaspartic acid, polybutadiene polyols, polyacrylate polyols, polyacrylic acid polyols, etc.

[0048] In some embodiments, in the two-component polyurethane coating composition, the molar ratio of the polyisocyanate composition, based on the -NCO group content, to the hydroxyl content in the hydroxyl resin is 1:0.9-1:1.1.

[0049] In some embodiments, in the two-component polyurethane coating composition, other components may be added to component A and / or component B according to application requirements, for example, leveling agents, other auxiliary agents, additives, etc. The specific selection and specific dosage of other components may be specifically adjusted and determined according to actual application requirements.

[0050] The polyisocyanate composition of the present invention exists as a curing agent in the polyurethane coating composition. The polyurethane coating composition is prepared based on the polyisocyanate composition of the present invention, especially by introducing the polyisocyanate composition of the present invention into a two-component polyurethane coating composition with an adhesive reactive to isocyanate groups as a main resin, so that a coating with significantly improved chemical resistance and good comprehensive properties such as pendulum hardness and bending strength can be obtained.

[0051] The present invention further provides a coating with improved chemical resistance, the coating being obtained by applying the polyurethane coating composition described above on the surface of a substrate. The coating can be a film layer formed by applying the polyurethane coating on the surface of a substrate in the fields of automobiles, wood products, etc. and using it as an adhesive.

[0052] The technical solution provided by the present invention has the following beneficial effects:

[0053] The polyisocyanate composition of the present invention is applied to polyurethane coatings, which is beneficial to improving the performance of the resulting coating film, and can make the resulting coating film have improved chemical resistance and hardness, while taking into account comprehensive properties such as good bending strength. DETAILED DESCRIPTION

[0054] In order to facilitate the understanding of the present invention, the present invention will be further described below in conjunction with examples. It should be understood that the following examples are only for a better understanding of the present invention and do not mean that the present invention is limited to the following examples.

[0055] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which the invention belongs. The term "and / or" as may be used herein includes any and all combinations of one or more of the associated listed items.

[0056] Where specific experimental steps or conditions are not specified in the examples, the corresponding conventional experimental steps or conditions in the art can be used. The reagents or instruments used without specifying the manufacturer are all conventional products that can be purchased commercially.

[0057] Description of the test method:

[0058] NCO content: NCO content is determined according to the method of GB / T 12009.4-2016;

[0059] Residual monomer content: According to the method of GB / T18583-2008, the residual monomer content in the reaction system is determined by gas chromatography;

[0060] Viscosity: obtained using a BrookField DVI Prime viscometer with an S21 spindle at 25°C;

[0061] In the present invention, the content (mol %) and equivalent ratio (molar ratio) of the thioallophthalate group and the isocyanurate group in the polyisocyanate composition can be 13 C NMR test. The specific test conditions are as follows:

[0062] 13 C NMR equipment: AVANCE600 (Bruker), equipped with BBO probe (Bruker);

[0063] Sample concentration: 30wt%;

[0064] Resonance frequency: 150MHz;

[0065] Displacement standard: 77.0ppm (CDCl 3 );

[0066] Pulse program: zgig30;

[0067] Spectral width: 240ppm;

[0068] Spectrum center: 100ppm;

[0069] Chemical shift of isocyanurate group: 148ppm; Chemical shift of thioallocarboxylate group: 173ppm and 153ppm; Chemical shift of iminooxadiazinedione group: 135ppm, 145ppm and 148ppm; Chemical shift of biuret group: 156ppm; Chemical shift of uretdione group: 157ppm; Chemical shift of thiocarbamate group: 167ppm, chemical shift of uretonimine group: 159ppm. In the embodiments and comparative examples, the content (% mole) of isocyanurate group refers to the total amount of isocyanurate group, thioallocarboxylate group and possible iminooxadiazinedione group, biuret group, uretdione group, thiocarbamate group and uretonimine group in the prepared polyisocyanate composition.

[0070] The equivalent ratio of the thioallophenate group to the isocyanurate group was calculated by the ratio of the integrated value near 148.5 ppm to (integrated value near 173 ppm+153 ppm) / 2.

[0071] Materials and reagents:

[0072] HDI: Hexamethylene diisocyanate, Wanhua Chemical Group Co., Ltd.;

[0073] PDI: Pentamethylene diisocyanate, Wanhua Chemical Group Co., Ltd.;

[0074] 1-Hexanethiol: Aladdin Reagents;

[0075] 1-Octanethiol: Aladdin Reagents;

[0076] 1-Dodecanethiol: Aladdin Reagents;

[0077] Tetramethylammonium hydroxide-2-ethylhexanoate: Kent Chemical Co., Ltd.;

[0078] Tetramethylammonium hydroxide pentahydrate: Inokai Technology Co., Ltd.;

[0079] Acetone: Inotech Technology Co., Ltd.

[0080] Polyacrylic acid polyol: ACR6780, Foshan Gaoming Tongde Chemical Co., Ltd.

[0081] Ethylene glycol bis(3-mercaptopropionate): Aladdin Reagents Company.

[0082] [Example 1]

[0083] 750g of PDI was added to a reaction kettle, stirred and heated to 50°C under a nitrogen atmosphere, and then 13.5g of 1-dodecanethiol was added to the reaction kettle and maintained at 50°C; 0.68g of tetramethylammonium hydroxide-2-ethylhexanoate solution (20wt%, acetone solution) was added dropwise to the system, and the NCO% of the reaction solution was tracked and measured. When the NCO% value dropped to 39.4%, 0.09g of dibutyl phosphate was added to terminate the reaction. The reaction solution was separated using a short-path evaporator (separation temperature 150°C, pressure 12Pa) to remove unreacted PDI monomers to obtain a polyisocyanate composition 1.

[0084] [Example 2]

[0085] 800g of PDI was added to a reactor, stirred and heated to 55°C under a nitrogen atmosphere, and then 8g of 1-dodecanethiol was added to the reactor and maintained at 55°C; 0.96g of tetramethylammonium hydroxide-2-ethylhexanoate solution (20wt%, acetone solution) was added dropwise to the system, and the NCO% of the reaction solution was tracked and measured. When the NCO% value dropped to 39.2%, 0.13g of dibutyl phosphate was added to terminate the reaction. The reaction solution was separated using a short-path evaporator (separation temperature 150°C, pressure 12Pa) to remove unreacted PDI monomers to obtain a polyisocyanate composition 2.

[0086] [Example 3]

[0087] 800g HDI was added to a reactor, stirred and heated to 70°C under a nitrogen atmosphere, and then 4g 1-dodecanethiol was added to the reactor and maintained at 70°C; 1.12g of tetramethylammonium hydroxide pentahydrate solution (5wt%, acetone solution) was added dropwise to the system, and the NCO% of the reaction solution was tracked and measured. When the NCO% value dropped to 40.2%, 0.04g of dibutyl phosphate was added to terminate the reaction. The reaction solution was separated using a short-path evaporator (separation temperature 150°C, pressure 12Pa) to remove unreacted HDI monomers to obtain a polyisocyanate composition 3.

[0088] [Example 4]

[0089] 900g of PDI was added to a reaction kettle, stirred and heated to 60°C under a nitrogen atmosphere, and then 3.6g of 1-hexyl mercaptan was added to the reaction kettle and maintained at 60°C; 0.95g of tetramethylammonium hydroxide-2-ethylhexanoate solution (20wt%, acetone solution) was added dropwise to the system, and the NCO% of the reaction solution was tracked and measured. When the NCO% value dropped to 47.6%, 0.13g of dibutyl phosphate was added to terminate the reaction. The reaction solution was separated using a short-path evaporator (separation temperature 155°C, pressure 10Pa) to remove unreacted PDI monomers to obtain a polyisocyanate composition 4.

[0090] [Example 5]

[0091] 800g of PDI was added to a reactor, stirred and heated to 55°C under a nitrogen atmosphere, and then 14.4g of 1-octanethiol was added to the reactor and maintained at 55°C; 0.72g of tetramethylammonium hydroxide-2-ethylhexanoate solution (20wt%, acetone solution) was added dropwise to the system, and the NCO% of the reaction solution was tracked and measured. When the NCO% value dropped to 37.5%, 0.10g of diisooctyl phosphate was added to terminate the reaction. The reaction solution was separated using a short-path evaporator (separation temperature 155°C, pressure 10Pa) to remove unreacted PDI monomers to obtain a polyisocyanate composition 5.

[0092] [Example 6]

[0093] 800g of PDI was added to a reactor, stirred and heated to 55°C under a nitrogen atmosphere, and then 10.25g of 1-dodecanethiol was added to the reactor and maintained at 55°C; 0.60g of tetramethylammonium hydroxide-2-ethylhexanoate solution (20wt%, acetone solution) was added dropwise to the system, and the NCO% of the reaction solution was tracked and measured. When the NCO% value dropped to 37.6%, 0.08g of diisooctyl phosphate was added to terminate the reaction. The reaction solution was separated using a short-path evaporator (separation temperature 160°C, pressure 10Pa) to remove unreacted PDI monomers to obtain a polyisocyanate composition 6.

[0094] [Example 7]

[0095] 750g of PDI was added to a reactor, stirred and heated to 55°C under a nitrogen atmosphere, and then 32.0g of 1-dodecanethiol was added to the reactor and maintained at 55°C; 1.58g of tetramethylammonium hydroxide-2-ethylhexanoate solution (20wt%, acetone solution) was added dropwise to the system, and the NCO% of the reaction solution was tracked and measured. When the NCO% value dropped to 37.2%, 0.22g of diisooctyl phosphate was added to terminate the reaction. The reaction solution was separated using a short-path evaporator (separation temperature 180°C, pressure 18Pa) to remove unreacted PDI monomers to obtain a polyisocyanate composition 7.

[0096] [Example 8]

[0097] 800g of PDI was added to a reactor, stirred and heated to 55°C under a nitrogen atmosphere, and then 42.8g of 1-dodecanethiol was added to the reactor and maintained at 55°C; 0.95g of tetramethylammonium hydroxide-2-ethylhexanoate solution (20wt%, acetone solution) was added dropwise to the system, and the NCO% of the reaction solution was tracked and measured. When the NCO% value dropped to 45.5%, 0.13g of phosphoric acid was added to terminate the reaction. The reaction solution was separated using a short-path evaporator (separation temperature 150°C, pressure 12Pa) to remove unreacted PDI monomers to obtain a polyisocyanate composition 8.

[0098] [Comparative Example 1]

[0099] 800g of PDI was added to a reactor, stirred and heated to 55°C under a nitrogen atmosphere, and then 80g of 1-dodecanethiol was added to the reactor and maintained at 55°C; 0.80g of tetramethylammonium hydroxide-2-ethylhexanoate solution (20wt%, acetone solution) was added dropwise to the system, and the NCO% of the reaction solution was tracked and measured. When the NCO% value dropped to 30.2%, 0.11g of diisooctyl phosphate was added to terminate the reaction. The reaction solution was separated using a short-path evaporator (separation temperature 150°C, pressure 12Pa) to remove unreacted PDI monomers to obtain a polyisocyanate composition A.

[0100] [Comparative Example 2]

[0101] The same procedure was followed as in Example 3, except that 1-dodecanethiol was not added to the reaction system. The remaining operations were followed as in Example 3.

[0102] Comparative Example 2 obtained a polyisocyanate composition B.

[0103] [Example 9]

[0104] 750g of PDI was added to a reactor, stirred and heated to 50°C under a nitrogen atmosphere, and then 7.95g of ethylene glycol bis(3-mercaptopropionate) was added to the reactor and maintained at 50°C; 0.68g of tetramethylammonium hydroxide-2-ethylhexanoate solution (20wt%, acetone solution) was added dropwise to the system, and the NCO% of the reaction solution was tracked and measured. When the NCO% value dropped to 38.4%, 0.09g of dibutyl phosphate was added to terminate the reaction. The reaction solution was separated using a short-path evaporator (separation temperature 150°C, pressure 12Pa) to remove unreacted PDI monomers to obtain a polyisocyanate composition C.

[0105] The index results of the polyisocyanate composition are listed in Table 1.

[0106] Table 1. Basic indicators of polyisocyanate composition products

[0107]

[0108]

[0109] The polyisocyanate compositions prepared in the above examples and comparative examples were mixed with a hydroxyl resin (Tongde ACR6780) at a NCO / OH molar ratio of 1:1, and then a mixed solvent of ethyl acetate / xylene (mass ratio of 1:1) was added for dilution to obtain a paint with a polyisocyanate composition content of 40 wt%. The polyisocyanate compositions of Examples 1-8 corresponding to the final paints were respectively labeled as paints 1 to 8, and the polyisocyanate compositions of Comparative Example 1, Comparative Example 2 and Example 9 corresponding to the final paints were respectively labeled as paints A, B, and C.

[0110] The prepared paint was tested for adhesion and other properties according to the following method:

[0111] (1) Chemical resistance: GB / T 23989 2009, the sample was placed in a constant temperature and humidity environment (temperature: 75°C, humidity: 50%) for 1 week, the weight was 1 kg, the wiping speed was 60 times / min, the wiping solvent was butanone, and the substrate was tinplate;

[0112] (2) Pendulum hardness test: GB / T 1730, the substrate used is glass plate;

[0113] (3) Adhesion grade test: GB / T 9286, the substrate used is tinplate;

[0114] (4) Bending strength: GB / T 11185-2009, Bending test for paints and varnishes (conical mandrel), the substrate used is tinplate.

[0115] The test results are shown in Table 2.

[0116] Table 2 Test results of paint properties

[0117]

[0118]

[0119] It can be seen from the performance test results in Table 1 and Table 2 that in the paints 1-8 and paint C obtained in Examples 1-9 of the present invention, a polyisocyanate composition in which the equivalent ratio of thioalloycarboxylate groups to isocyanurate groups is controlled to be greater than 0 and less than 0.3 is used, and the final paints can take into account excellent chemical resistance, pendulum hardness and bending strength; while the chemical resistance and pendulum hardness of the paints A and B obtained in Comparative Examples 1 and 2 are significantly inferior to those of the paints obtained in the examples, and cannot take into account good chemical resistance, pendulum hardness and bending strength at the same time.

[0120] In Examples 1-8, while controlling the equivalent ratio of thioalloycarboxylate groups to isocyanurate groups in the polyisocyanate composition to be greater than 0 and less than or equal to 0.3, monohydric thiol is used in the preparation of the polyisocyanate composition. As a result, the resulting paints, compared with the paint of Example 9 which does not use monohydric thiol, not only have excellent chemical resistance, pendulum hardness and bending strength, but also have excellent adhesion, while Example 9 cannot have excellent adhesion at the same time.

[0121] Compared with Examples 1-7, the equivalent ratio of thioalloylate groups to isocyanurate groups in the polyisocyanate composition of Example 8 is not within the more preferred range of 0.005-0.100, and the performance of the resulting paint is inferior to that of the paints obtained in Examples 1-7.

[0122] It is easy to understand that the above embodiments are only examples for clear explanation and do not mean that the present invention is limited thereto. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from this are still within the protection scope of the present invention.

Claims

1. A polyisocyanate composition, wherein the polyisocyanate composition is derived from at least one diisocyanate selected from aliphatic diisocyanates and alicyclic diisocyanates, wherein at least some of the compounds contained in the polyisocyanate composition have isocyanurate groups, and at least some of the compounds have at least one thioallophanate group; characterized in that: In the polyisocyanate composition, the equivalent ratio of the thioallophenate group to the isocyanurate group is greater than 0 and less than or equal to 0.

3.

2. The polyisocyanate composition according to claim 1, characterized in that In the polyisocyanate composition, the equivalent ratio of the thioallophenate group to the isocyanurate group is 0.005-0.250, more preferably 0.005-0.

100.

3. The polyisocyanate composition according to claim 1 or 2, characterized in that In the polyisocyanate composition, the content of the isocyanurate groups is ≥90 mol % and <100 mol %, based on the total amount of the isocyanurate groups and thioalloylate groups in the composition and the optionally present iminooxadiazinedione groups, biuret groups, uretdione groups, thiocarbamate groups and uretonimine groups.

4. The polyisocyanate composition according to any one of claims 1 to 3, characterized in that The polyisocyanate composition can be obtained by reacting a reaction mass comprising the diisocyanate and a thiol compound, wherein the thiol compound is selected from at least one linear or branched and optionally substituted thiol compound; preferably, the group in the thiol compound that is reactive toward an isocyanate group is a thiol group.

5. The polyisocyanate composition according to claim 4, characterized in that The mercapto compound has 1 to 20 carbon atoms, preferably 6 to 12 carbon atoms; Preferably, the thiol compound is one or more of monohydric thiol and polyhydric thiol, more preferably monohydric thiol; Further preferably, the thiol compound is selected from one or more of 1-hexanethiol, 2-hexanethiol, 3-hexanethiol, 1-methylpentane-2-thiol, 3,3-dimethylbutane-1-thiol, 2-ethyl-butane-1-thiol, 1-methyl-1-pentanethiol, 3-methylpentane-2-thiol, 1-heptanethiol, 2-heptanethiol, 1-octanethiol, 2-octanethiol, 2-ethyl-1-hexanethiol, 1-nonanethiol, 2-nonanethiol, 1-decanethiol, 3-decanethiol, 1-undecanethiol, undec-10-ene-1-thiol, 1-dodecanethiol, 2-dodecanethiol, and tert-dodecanethiol.

6. The polyisocyanate composition according to any one of claims 1 to 5, characterized in that: The diisocyanate is selected from one or more of hexamethylene diisocyanate, pentamethylene diisocyanate, 2-methylpentane-1,5-diisocyanate, 2,4,4-trimethyl-1,6-hexane diisocyanate, 2,2,4-trimethyl-1,6-hexane diisocyanate, 4-isocyanatomethyl-1,8-octane diisocyanate, 3-isocyanatomethyl-1-methylcyclohexyl isocyanate, 4-isocyanatomethyl-1-methylcyclohexyl isocyanate, isophorone diisocyanate, 1,3-bis(isocyanatomethyl)cyclohexane and 1,4-bis(isocyanatomethyl)cyclohexane, preferably one or two of hexamethylene diisocyanate and pentamethylene diisocyanate.

7. The polyisocyanate composition according to any one of claims 4 to 6, characterized in that: The reaction is carried out in the presence of a catalyst; the amount of the catalyst is preferably 0.001-0.1 wt % of the diisocyanate used to prepare the polyisocyanate composition, more preferably 0.005-0.05 wt %; Preferably, the catalyst is selected from one or more of quaternary ammonium hydroxides, quaternary ammonium carboxylates, aminosilyl-containing compounds, tertiary amine compounds, and Mannich base compounds; Further, the quaternary ammonium hydroxide is, for example, selected from one or more of tetramethylammonium hydroxide, trimethylbenzylammonium hydroxide, tetraethylammonium hydroxide, dimethylethylcyclohexylammonium hydroxide and hydrates thereof; Further, the quaternary ammonium carboxylate is, for example, selected from tetramethylammonium hydroxide-2-ethylhexanoate, tetramethylammonium hydroxide-octanoate, trimethylbenzylammonium hydroxide-2-ethylhexanoate, trimethylbenzylammonium hydroxide-octanoate, tetramethylammonium hydroxide-formate, tetramethylammonium hydroxide-acetate, tetramethylammonium hydroxide-pivalate, trimethylbenzylammonium hydroxide-pivalate, tetramethylammonium hydroxide-decanoate, trimethylbenzylammonium hydroxide-decanoate, tetramethylammonium hydroxide-tetradecanoate, tetramethylammonium hydroxide-2-ethylhexanoate, tetramethylammonium hydroxide-octanoate, trimethylbenzylammonium hydroxide-2-ethylhexanoate, and one or more of trimethylbenzylammonium hydroxide-octanoate; Furthermore, the aminosilyl-containing compound is, for example, one or more selected from hexamethyldisilazane, silylamine, and heptamethyldisilazane; Furthermore, the tertiary amine compound is selected from one or two of triethylamine and tripropylamine; Furthermore, the Mannich base compound is, for example, tris(N,N-dimethylaminomethyl)phenol.

8. The polyisocyanate composition according to any one of claims 4 to 7, characterized in that: The reaction temperature of the reaction is 10-150°C, preferably 30-79°C, more preferably 45-75°C; And / or, the reaction endpoint of the reaction is that the NCO% value of the reaction system is in the range of 30-50%.

9. Use of the polyisocyanate composition according to any one of claims 1 to 8 as a crosslinking agent in a coating composition.

10. A two-component polyurethane coating composition, characterized in that: The invention comprises component A and component B, wherein component A comprises at least one polyisocyanate composition according to any one of claims 1 to 8, and component B comprises at least one binder reactive to isocyanate groups.

11. A coating with improved chemical resistance, characterized in that The coating is obtained by applying the polyurethane coating composition according to claim 10 on the surface of a substrate.

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